Arc shield



W. H. KEMPTON.

ARC SHIELD.

APPLICATION FILED JULY 25, 1918.

1,481,961', Patented Oct. 17, 1922.

ATTORNEY stantially 50% carborundum, 10% asbestos Patented Oct. 17, 1922.

UNITED STATES 1,431,961 PATENT OFFICE.

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VAIIA.

To all whom 'it may conc-em:

Be it known that I, WILLARD H. KEMP'roN, a citizen of the United States, and a resident of Wilkinsbur in the county of Allegheny and State o Pennsylvania, have invented a new and useful Improvement in Arc Shields, of which the following is a specilication.

My invention relates to arc shields, and it has for its primary object the provision of a hi hly refractory arc-resistive material whicl may be employed in the construction of arc shields.

One object of my invention is to provide a composite arc shield consisting of two materials which shall have substantially the same coelicient of expansion.

Another object of my invention is to provide a composite arc shield composed of two materials which will yield readily to the same treatment in the process of manufacure.

A still further object of my invention is to provide an arc shield comprising two compositions one of which is specially adapted to resist the action of arcs and to localize such composition at a predetermined portion of the arc shield which will be exposed to arcs.

With these and other objects in view, a

better understanding of my invention may be had by reference to the drawings in which Fi 1 is a plan view of an are shield emboying my lnvention, and Fig. 2 is a section taken on the line II-II of Fig. 1. In practicing my invention, I employ a composition comprising three ingredients which, when thoroughly mixed and molded and then treated, are so united and of such nature as to offer great resistance to electric arcs. Another course which may be followed in practicinglmy invention is to employ the aforesaid ingredients which form an efficient arc shield and mold these ingredients together with another composition so that the composition which is highly resistant to arcs shall be concentrated at a portion of the shield exposed to the arcs.

In Fig. 1 is shown one form of a shield 1 which may be composed of a moldable composition 2 comprising approximatel 50% asbestos and 50% Portland cement, an a moldable material 3, which may be concentrated at one portion of the shield and may consist of subfibre, and 40% Portland cement. The material 2 1s thorou hly mixed with suilicient water and placed 1n a mold, a space being reserved to receive the material 3, which is similarly mlxed. The two compositions may then be sub]ected .to suicient ressure to insure a perfect shield, after whlch the formed shield 1s removed from the mold and subjected to heatin curing and drying processes to remove ail moisture from its composition. The heating, curing and drying processes may mvolve the use of a steam bath in which the molded shield is placed for three days a'fter which it is removed Vand exposed to dry air for twenty-.four hours and then subjected to vacuum drylng for three hours at a temperature of about 60 C. The body thus bullt up may then be covered with a suitable waterproof coating, if desired, although the waterproof coatin is not absolutely necessary to roduce e ciency on the part of the shield. t 1s, however, customary to coat the sh1e1d 1n this way to prevent any absorption ofmolsture in the event of the shield being out of use for a long riod. The shield may be formed entirely o the com ition designated by the numeral 3 if so esired. This, however, is a more expensive form of shield and 1s unnecessary for the reason that the pomt which the arc will strike ma be predeternuned and, therefore, the s ield reu 1res the highly resistive material only at t 1s point. The material 2 employed in the construction of the shield, as shown, being cheaper and yielding readily to the same treatment as t e material 3 is, therefore, advanta ous.

Alt ough I have shown one form of an are shield that may be constructed in accordance with my invention, it is obvious that the ingredients thereof may be slightly varied without departing from the spirit of my invention an I desire, therefore, that no limitations shall be imposed except such as are indicated in the appended claims.

I claim as m invention:

1. An arc `slueld comprising carborundum, Portland cement and asbestos.

2. An arc shield comprising substantially 50%l carborundum, 40% Portland cement and 10% asbestos fibre.

3. An arc shield comprising a. body portion composed of current and heat-resisting material and an insert of highly refractory arc-resistive material.

4. A molded arc shield comprising a body portion composed of current and heat-resisting material and an insert of highly refractory arc-resistive material.

5. An arc shield comprising a body portion formed of current and heat-resisting material and a localized portion composed of carborundum, Portland cement and asbestos fibre.

6. An arc shield comprising a body porwhich comprises molding a body composed in part of heat and current-resisting material and a localized portion of arc-resisting material and curing the molded body.

10. vA method of constructing arc shields -which comprises mixing Portland cement and asbestos, adding sufficient water thereto, placing the resulting composition in a mold, reserving a space therein, mixing carborundum, Portland cement and asbestos with water, filling the reserved space with the mixed composition of carborundum, Portland cement and asbestos, subjecting the two compositions to suficient pressure to form a Solid piece, removing the molded piece from the mold and subjecting it to curing, heating and drying processes.

11. A method of constructing arc shields which comprises mixing substantially equal quantities of Portland cement and asbestos, adding sufficient water thereto, placing the resulting composition in a mold, reserving a space therein, mixing approximately 50% carborundum, 40% l ortland cement and 10%asbestos with Water, filling the reserved space with a mixed composition of the abovementioned proportions of carborundum, Portland cement and asbestos, and subjecting the two compositions to sufficient pressure to form a solid piece, removing the molded piece from the mold and subjecting it to curing, heating and d ing processes.

In testimony whereof, have hereunto subscribed my name this 22nd day of July WILLARD H; KEMPTON. 

